﻿using System;
using System.Collections.Generic;
using System.Globalization;
using Svg.DataTypes;
using Svg.FilterEffects;
using Svg.Model.Drawables;
using Svg.Model.Drawables.Elements;
#if USE_SKIASHARP
using SkiaSharp;
#else
using ShimSkiaSharp;
#endif

namespace Svg.Model;

public static partial class SvgExtensions
{
    internal static SKColor s_transparentBlack = new(0, 0, 0, 255);

    internal static bool IsNone(this Uri uri)
    {
        return string.Equals(uri.ToString(), "none", StringComparison.OrdinalIgnoreCase);
    }

    private static byte[] s_Identity => new byte[256]
    {
        0,   1,   2,   3,   4,   5,   6,   7,   8,   9,   10,  11,  12,  13,  14,  15,
        16,  17,  18,  19,  20,  21,  22,  23,  24,  25,  26,  27,  28,  29,  30,  31,
        32,  33,  34,  35,  36,  37,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,
        48,  49,  50,  51,  52,  53,  54,  55,  56,  57,  58,  59,  60,  61,  62,  63,
        64,  65,  66,  67,  68,  69,  70,  71,  72,  73,  74,  75,  76,  77,  78,  79,
        80,  81,  82,  83,  84,  85,  86,  87,  88,  89,  90,  91,  92,  93,  94,  95,
        96,  97,  98,  99,  100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
        112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
        128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143,
        144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159,
        160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175,
        176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191,
        192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207,
        208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223,
        224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239,
        240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255,
    };

    // Precomputed sRGB to LinearRGB table.
    // if (C_srgb <= 0.04045)
    //     C_lin = C_srgb / 12.92;
    //  else
    //     C_lin = pow((C_srgb + 0.055) / 1.055, 2.4);
    private static byte[] s_sRGBtoLinearRGB => new byte[256]
    {
        0,   0,   0,   0,   0,   0,  0,    1,   1,   1,   1,   1,   1,   1,   1,   1,
        1,   1,   2,   2,   2,   2,  2,    2,   2,   2,   3,   3,   3,   3,   3,   3,
        4,   4,   4,   4,   4,   5,  5,    5,   5,   6,   6,   6,   6,   7,   7,   7,
        8,   8,   8,   8,   9,   9,  9,   10,  10,  10,  11,  11,  12,  12,  12,  13,
        13,  13,  14,  14,  15,  15,  16,  16,  17,  17,  17,  18,  18,  19,  19,  20,
        20,  21,  22,  22,  23,  23,  24,  24,  25,  25,  26,  27,  27,  28,  29,  29,
        30,  30,  31,  32,  32,  33,  34,  35,  35,  36,  37,  37,  38,  39,  40,  41,
        41,  42,  43,  44,  45,  45,  46,  47,  48,  49,  50,  51,  51,  52,  53,  54,
        55,  56,  57,  58,  59,  60,  61,  62,  63,  64,  65,  66,  67,  68,  69,  70,
        71,  72,  73,  74,  76,  77,  78,  79,  80,  81,  82,  84,  85,  86,  87,  88,
        90,  91,  92,  93,  95,  96,  97,  99, 100, 101, 103, 104, 105, 107, 108, 109,
        111, 112, 114, 115, 116, 118, 119, 121, 122, 124, 125, 127, 128, 130, 131, 133,
        134, 136, 138, 139, 141, 142, 144, 146, 147, 149, 151, 152, 154, 156, 157, 159,
        161, 163, 164, 166, 168, 170, 171, 173, 175, 177, 179, 181, 183, 184, 186, 188,
        190, 192, 194, 196, 198, 200, 202, 204, 206, 208, 210, 212, 214, 216, 218, 220,
        222, 224, 226, 229, 231, 233, 235, 237, 239, 242, 244, 246, 248, 250, 253, 255,
    };

    // Precomputed LinearRGB to sRGB table.
    // if (C_lin <= 0.0031308)
    //     C_srgb = C_lin * 12.92;
    // else
    //     C_srgb = 1.055 * pow(C_lin, 1.0 / 2.4) - 0.055;
    private static byte[] s_linearRGBtoSRGB => new byte[256]
    {
        0,  13,  22,  28,  34,  38,  42,  46,  50,  53,  56,  59,  61,  64,  66,  69,
        71,  73,  75,  77,  79,  81,  83,  85,  86,  88,  90,  92,  93,  95,  96,  98,
        99, 101, 102, 104, 105, 106, 108, 109, 110, 112, 113, 114, 115, 117, 118, 119,
        120, 121, 122, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136,
        137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 148, 149, 150, 151,
        152, 153, 154, 155, 155, 156, 157, 158, 159, 159, 160, 161, 162, 163, 163, 164,
        165, 166, 167, 167, 168, 169, 170, 170, 171, 172, 173, 173, 174, 175, 175, 176,
        177, 178, 178, 179, 180, 180, 181, 182, 182, 183, 184, 185, 185, 186, 187, 187,
        188, 189, 189, 190, 190, 191, 192, 192, 193, 194, 194, 195, 196, 196, 197, 197,
        198, 199, 199, 200, 200, 201, 202, 202, 203, 203, 204, 205, 205, 206, 206, 207,
        208, 208, 209, 209, 210, 210, 211, 212, 212, 213, 213, 214, 214, 215, 215, 216,
        216, 217, 218, 218, 219, 219, 220, 220, 221, 221, 222, 222, 223, 223, 224, 224,
        225, 226, 226, 227, 227, 228, 228, 229, 229, 230, 230, 231, 231, 232, 232, 233,
        233, 234, 234, 235, 235, 236, 236, 237, 237, 238, 238, 238, 239, 239, 240, 240,
        241, 241, 242, 242, 243, 243, 244, 244, 245, 245, 246, 246, 246, 247, 247, 248,
        248, 249, 249, 250, 250, 251, 251, 251, 252, 252, 253, 253, 254, 254, 255, 255,
    };

    // Convert 0..1 linear value to 0..1 srgb.
    internal static float LinearToSRGB(float linear)
    {
        if (linear <= 0.0031308)
        {
            return linear * 12.92f;
        }

        return 1.055f * (float)Math.Pow(linear, 1f / 2.4f) - 0.055f;
    }

    // Convert 0..1 srgb value to 0..1 linear.
    internal static float SRGBToLinear(float srgb)
    {
        if (srgb <= 0.04045f)
        {
            return srgb / 12.92f;
        }

        return (float)Math.Pow((srgb + 0.055f) / 1.055f, 2.4f);
    }

    internal static SKColorFilter LinearToSRGBGamma()
    {
        return SKColorFilter.CreateTable(s_Identity, s_linearRGBtoSRGB, s_linearRGBtoSRGB, s_linearRGBtoSRGB);
    }
    
    internal static SKColorFilter SRGBToLinearGamma()
    {
        return SKColorFilter.CreateTable(s_Identity, s_sRGBtoLinearRGB, s_sRGBtoLinearRGB, s_sRGBtoLinearRGB);
    }
}
